Resistance device



Jan. 28, 1930. Q MA v 1,744,911

- QESISTANCE DEVICE Filed Jan. 11. 1 928 Oldrz'eh 1 Masin IN V EN TOR.

ULIDRECH IE. MASIN, OF NEW YORK, N. Y., ASSIGNOR T WARD LEONARD ELECTRIC COMPANY, A CORPORATION OF NEW YORK RESISTANCE DEVICE Application filed January 11, 1928. Serial No. 245,829.

This invention relates to resistance devices, more particularly to a light weight resistance device for heating units adapted to heat up quickly and to cool 01f correspondingly 5 quickly. This invention also relates to an improved method of manufacturing.

in the prior forms of resistance devices wherein the resistive conductor is wound upon a hollow tube of porcelain, pottery or like material and covered with enamel, it has been difficult to construct resistance devices wherein the resistance in the device could be determined with accuracy because of the difference in expansion between the resistive conductor and the porcelain or pottery tube upon heating to fuse the enamel.

Devices of this prior form are constructed by winding the resistive conductor on a porcelain or pottery tube, vitreous enamel being applied thereto -in powdered form and thereafter placing the device in a furnace for fusing the enamel. During the heating the resistive conductor expands much more than the porcelain with the result that the turns of the resistive conductor readily expand when heated and become loose on the tube, permitting the molten enamel to flow between the resistive conductor and the tube. When the unit is withdrawn from the furnace and begins to cool, the diameter of the tube plus the enamel between the turns of the resistive conductor is greater than before heating and the contracting of the wire stretches it and it necessarily becomes a longer wire of less cross sectional area than when originally wound on the tube, resulting in an increased resistance in the device. This construction is objec tionable for some purposes as it is extremely diflicult to accurately determine beforehand the resistance in the completed device.

Resistance devices of this prior form neces" sarily have the tube of porcelain or like material constructed of considerable thickness to obtain the necessary strength which results in giving the unit considerable weight which is undesirable for some uses. This construction is also objectionable for some uses because owing to the thickness of the porcelain or pottery tube the device will not heat up quickly and cool off correspondingly quickly.

The main object of this invention is to not only provide an improved method of making the resistance device but also to provide an improved resistance device wherein the resistive conductor is wound on an insulating tubing and so constructed that the resistance in the device can be accurately determined beforehand.

A further object of the invention is to provide a resistance device so constructed that it heats up readily and at the same time being light weight.

A. still further object of the invention is to provide a resistance device with both of the lead terminals located at one end.

A still further object of the invention is to provide a resistance device wherein the interior diameter of the supporting tube is accurately gauged and adapted to be slipped over its support and make a close fit, and also to provide a resistance device especially adapted for heating units such as used in permanent waving machines and the like.

Further objects and advantages of the invention will be apparent from the following specification and drawings, in which Fig. 1 is a view of the resistance device of this invention showing the first step in forming the tubing and winding the resistive conductor thereon.

Fig. 2 is a View of the resistance device with one lead wire attached thereto.

Fig. 3 is a view of the resistance device before coating.

Fig. 4 is a view of the resistance device with its insulating coating and ready to be withdrawn from its supporting mandrel, and

Fig. 5 is an enlarged sectional View on line 55 of Fig. 4.

In attaining these objectsI provide a mandrel upon which is wound a sheet of mica or like material to form a tube around which is wound the resistive conductor. The resistive conductor is then coated with an insulating material such as-vitreous enamel and fused. During the fusing process the mica tube wound upon the mandrel expands approximately the same as the resistive conductor. Therefore there is no stretching of the resistive conductor upon cooling of the device which would change the resistance of the device. Thus it will be readily seen that the resistance of the device can be accurately determined as the heating process for fusing the enamel does not disturb the resistive conductor in any manner.

The resistance device is built up on a slight 1y tapered hollow mandrel 10 of brass or other proper material having an enlarged end portion 11 for attachment to a rotating chuck. The insulating supporting base on which the resistive conductor 12 is wound is constructed of a sheet of mica or like insulating material 13, cut to a suitable size and rolled or wound upon the mandrel 10. The sheet of mica 13 is wound around the mandrel 10 any desired suitable number of times to form a tube. The loose end or edge 14 of the mica sheet before being placed in final position, has inserted beneath it and running longitudinally of the mandrel 10, one end of the resistive conductor 12, as shown in Fig. 1. After the loose end 14: of the mica sheet is placed over the end of the I conductor 12 and held in place by any clamping means such as a piece of string, not shown, one end 15 of the conductor is then wound around the terminal wire 16 to provide an electrical connection 17. The terminal Wire 16 is then wound around the mica tube and held in position by connection 18 which is formed by twisting the wire together as shown in Figs. 2 and 3. It will be readily seen that the resistive conductor 12 runs the entire length of the mica tube beneath the top layer of the mica sheet. The outer sheet of the mica is formed at the end opposite from the terminal wire, with a small slit 19 through which the resistive conductor is brought out, as shown in Figs. 2 and 3. The resistive conductor is then wound back along the outside of the mica tube the required number of times to give the desired resistance and the end connected to a second terminal wire 20 at 21, as shown in Fig. 3. This terminal wire is also wound around the mica tube and held in position by twisting the terminal wire as shown at 22. The location of this twist and of the terminal wire 20 may be diametrically opposite from the connection 18 and the terminal wire 16. This construction locates the terminals of the resistive conductor both at one end of the device with the resistive conductor properly insulated by the mica tube, as shown in Fig. 3.

The resistance device, when constructed in the manner described and shown in Fig. 3, is then coated with a coating of suitable insulating material such as vitreousenamel 23.

The firing or heating in a furnace to form the enamel is done while the tube remains on the mandrel. The mandrel 10 is slightly tapered and may be made of a metal such as brass 'which oxidizes slightly during the firing process so that the completed resistance devlce can be readily withdrawn from the mandrel without injury to the mica tube. This method of construction on a proper size of mandrel gives a tube of a smooth interior surface, the inner diameter of whichis ac curately gauged according to the mandrel selected.

While one form of this invention is illustrated and described herein, the invention may be embodied in various modifications without departing from the scope of the appended claims.

I claim:

1. The method of making a resistance device which consists in applying insulating material on a mandrel to form a tube, winding a resistive conductor around said tube, applying a coating of insulating material to said device, hardening said coating, and then removing said mandrel from within said tube.

2. The method of making a resistance device which consists in applying insulating material on a mandrel to form a tube, winding a resistive conductor around said tube, applying a coating of enamel material to said device, heating to form a vitreous enamel coating, and then removing said mandrel from within said tube.

3. The method of making a resistance device which consists in winding a sheet of material on a mandrel to form a tube, winding a resistive conductor around said tube, applying a coating of enamel material to said device, fusing said material by heating said device to form a vitreous enamel coating, and then removing said mandrel from within said tube.

4. The method of making a resistance device which consists in winding a resistive conductor on a tube supported on a mandrel, applying a coating of insulating material to said device and heating said device to fuse said material, then removing said mandrel from within said tube, said mandrel and tube having substantially the same coeflicient of expansion as said resistive conductor.

5. The method of making a resistance device which consists in windin a sheet of insulating material on a man rel to form a tube, attaching one end of a resistive conductor at one end of the tube, inserting said conductor longitudinally of said tube between the layers of said sheet material, winding said conductor around said tube in a direction toward said attached end, attaching the second end of said conductor adjacent the said first end of said conductor and applying a coating of insulating material to said device. 3

6. The method of making a resistance device which consists in winding a sheet of insulating material on a mandrel to form a tube, inserting a longitudinally extending resistive conductor between the layers of said tube, fixing one end of said conductor to a terminal wound around one end of said tube, winding said conductor upon said tube in a direction toward said terminal over said con ductor located between the layers of said tube, fixing the second end of said conductor to a second terminal wound around the same end of said tube as the first mentioned terminal wire adjacent to and spaced from said first mentioned terminal wire, and applying a coating of insulating material over said conductor and a portion of said terminals, hardening said coating, and then removing said mandrel from within said tube.

7. The method of making a resistance device which consists in winding a sheet of insulating material in overlapping layers on a mandrel to form a tube, inserting a longitudinally extending resistive conductor beneath a layer of said sheet material, connecting one end of said conductor to a terminal wire, winding said terminal around said tube at one end of said tube, winding said conductor from the opposite end of said tube where it comes out from beneath the layer of sheet material, attaching the other end of said conductor to a second terminal, winding said terminal wire about said tube at the same end as the first mentioned terminal, applying a coating of insulating material over said conductor tube, and the portion of said terminal wires wound around'said tube, fusing said coating, and then removing said material from within said tube.

8. A resistance device comprising an insulated support formed in layers of sheet material and having a central axis, and a resistive conductor, one end portion of which extends longitudinally in a position offset from said axis between layers of said sheet material and a second portion of which is wound on said support over the outer layer of saidmaterial.

9. In a resistance device, an insulating support comprising sheet material wound in layers to form a tube, terminals encircling said tube adjacent one end thereof, and a resist-ive conductor fixed to said terminals at its ends, one portion of which extends longitudinally in a position offset from the axis of the tube and between layers of said sheet material and a second portion of which is wound around the outer layer of sheet material.

10. In a resistance device an insulating support comprising sheet mica wound in layers to form a tube, terminals encircling said tube adjacent one end thereof, and a resistive conductor fixed to said-terminal at its ends, one portion of which is inserted between sa d layers lengthwise of said tube and in a pos1 tion offset from the axis of the tube and a second portion wound around said tube.

11. In a resistance device an insulating support comprising sheet material wound in layers to form a tube, terminals at one end of said tube, a resistive conductor attached OLDRIGH F. NASIN. 

